1. Field of the Invention
The present invention relates to a dry vacuum pump, and in particular to an improved dry vacuum pump which is capable of increasing a discharging speed of a gas compressed and discharged, adjusting a vacuum degree of a vacuum pump and concurrently cooling a friction element of a vacuum pump and a gas pumped.
2. Description of the Background Art
In a screw type vacuum pump, a pair of screws are installed in the interior of a cylinder. A gas is drawn in from a vacuum facility and is compressed as the screws are engaged and rotated. The compressed gas is discharged to the outside, thereby implementing a vacuum state within the gas pump. In order to quickly obtain a high vacuum state, a plurality of sub-vacuum pumps each having a rotor are continuously installed in such a manner that a compression ratio of the same is gradually increased in the direction of an outlet. In the above vacuum pump, a high temperature heat is generated in a screw and a bearing portion that supports a rotary shaft of a rotor. When the gas is compressed to a high pressure state, since the gas causes the surrounding components to become over-heated, various friction elements which form a vacuum pump are easily degraded and worn-out, so that a durability of the system is decreased.
In order to overcome the above problems, in the conventional vacuum pump, a cooling water flow path is formed outside a gas flow path formed in the interior of the cylinder, so that the temperature of the gas which flows through the gas flow path is cooled by cooling water which circulates through a cooling water flow path.
In the above method, the operation for cooling a high temperature compression gas which flows through the gas flow path is effective. However, since the cooling water flow path is distanced from the portion of the rotary shaft, the portions of the rotary shaft in which a high friction heat is generated due to a high speed rotation member, e.g., such as bearing, are not effectively cooled.
In addition, in the conventional vacuum pump, since the screw has an one-line threaded portion, it is impossible to increase the discharging speed of the gas pumped from the vacuum pump. Since it is impossible to vary the vacuum degree of the vacuum pump based on a pumping situation, it is impossible to implement a desired performance of the vacuum pump in which a high vacuum degree must be obtained during a short pumping time.
Accordingly, it is an object of the present invention to provide a dry vacuum pump that overcomes the problems encountered in a conventional cylindrical pump housing structure.
It is another object of the present invention to provide a dry vacuum pump which is capable of increasing a discharging speed of a gas which is compressed and discharged by forming a threaded portion of a main screw in multiple portions, sequentially installing a plurality of cylinders each having a gas discharging rotor as a sub-vacuum pump in a rear end of a cylinder having a main screw for thereby adjusting a vacuum degree of a vacuum pump and forming a cooling water flow path between shafts which form a vacuum pump for thereby concurrently cooling or offsetting heat generated in a rotation friction element of a vacuum pump and a high temperature gas which is pumped.
To achieve the above object, there is provided a dry vacuum pump comprising a first cylinder and a second cylinder being installed between a front cover and a rear cover in a tier-structure; an intermediate cover being formed between the first and the second cylinders; a main screw being installed in the first cylinder for compressing and discharging a gas of a vacuum facility; a rotor being formed in the second cylinder for drawing, compressing, and discharging the gas compressed by the main screw; a gas flow path being formed between the intermediate cover and the second cylinder for compressing and discharging the gas; a motor housing engaging the front cover; a cooling water inlet being formed within an outer surface of the rear cover of the dry vacuum pump; a cooling water outlet being formed within the front cover; a cooling flow path being formed for guiding the cooling water pumped through the cooling water inlet to circulate in each cylinder and intermediate cover; wherein the cooling water flow path is formed in an inner and an outer side of the gas flow path formed in the rear cover and intermediate cover and in a circular shape; and a flow pipe, wherein the cooling water flow path which is formed in the inner and outer sides of the gas flow path is connected by the flow pipe which passes through the gas flow path for thereby concurrently cooling the gas flow path and portions of a rotary shaft by a cooling water which flows through the cooling water flow path.
In the present invention, a threaded portion of the main screw is formed with multiple threads for thereby increasing a discharging speed of the gas pumped.
In addition, a cooling water circulation hole is formed in an outer portion of the motor housing in a screw shape, and one side of the cooling water circulation hole is connected with the cooling water outlet of the front cover through a connection pipe, and the other side of the cooling water circulation hole is connected with a water pump through a cooling water flow pipe.